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TypeScriptとlibvipsで、画像処理100本ノックに挑戦（001/100）
これはなに？
下記の画像処理100本ノックを、TypeScriptとlibvipsで挑戦してみる記事です。
経緯
今後のキャリアでTypeScriptをメインで触りそうだと感じています。今まではCやRubyなどでコードを書いてきました。TypeScriptに慣れるために、自分の興味がある領域からコードを書き始めれば勘所を掴めるかと思い始めてみました。
libvipsについて
libvipsは、OpenCVやImageMagickなどと同じ画像処理を行うライブラリです。
高速かつ省メモリが特徴になります。
100本ノックをするさいに、OpenCVを利用しても良かったのですが、今回の用途には機能が過剰すぎることと学生時代に十分利用しましたので、別のライブラリで試してみたかったのが選定理由です。
準備
まずは環境を構築します。
環境
当方の作業環境は以下の通りです。
OS：macOS 15.2（24C101）
チップ:Apple M1
npm：10.2.4
node:v23.5.0
環境構築
今回は vips-image-processing という名前のプロジェクトに決めました。
# プロジェクト用の新しいディレクトリを作成して移動
mkdir vips-image-processing
cd vips-image-processing
# package.jsonの初期化
npm init -y
必要なパッケージのインストールします。
# TypeScriptと必要なライブラリをインストール
npm install typescript @types/node ts-node sharp @types/sharp
# libvipsをHomebrewでインストール
brew install vips
今回は、Node.js用のバインディングとして広く利用されている sharp を利用します。
また、ローカル環境にlibvipsがインストールされていない場合は、インストールも行います。
TypeScriptの設定を行います。
# TypeScript設定ファイルを生成
npx tsc --init
{
"compilerOptions": {
/* Visit https://aka.ms/tsconfig to read more about this file */
/* Projects */
// "incremental": true, /* Save .tsbuildinfo files to allow for incremental compilation of projects. */
// "composite": true, /* Enable constraints that allow a TypeScript project to be used with project references. */
// "tsBuildInfoFile": "./.tsbuildinfo", /* Specify the path to .tsbuildinfo incremental compilation file. */
// "disableSourceOfProjectReferenceRedirect": true, /* Disable preferring source files instead of declaration files when referencing composite projects. */
// "disableSolutionSearching": true, /* Opt a project out of multi-project reference checking when editing. */
// "disableReferencedProjectLoad": true, /* Reduce the number of projects loaded automatically by TypeScript. */
/* Language and Environment */
"target": "es2016", /* Set the JavaScript language version for emitted JavaScript and include compatible library declarations. */
// "lib": [], /* Specify a set of bundled library declaration files that describe the target runtime environment. */
// "jsx": "preserve", /* Specify what JSX code is generated. */
// "experimentalDecorators": true, /* Enable experimental support for legacy experimental decorators. */
// "emitDecoratorMetadata": true, /* Emit design-type metadata for decorated declarations in source files. */
// "jsxFactory": "", /* Specify the JSX factory function used when targeting React JSX emit, e.g. 'React.createElement' or 'h'. */
// "jsxFragmentFactory": "", /* Specify the JSX Fragment reference used for fragments when targeting React JSX emit e.g. 'React.Fragment' or 'Fragment'. */
// "jsxImportSource": "", /* Specify module specifier used to import the JSX factory functions when using 'jsx: react-jsx*'. */
// "reactNamespace": "", /* Specify the object invoked for 'createElement'. This only applies when targeting 'react' JSX emit. */
// "noLib": true, /* Disable including any library files, including the default lib.d.ts. */
// "useDefineForClassFields": true, /* Emit ECMAScript-standard-compliant class fields. */
// "moduleDetection": "auto", /* Control what method is used to detect module-format JS files. */
/* Modules */
"module": "commonjs", /* Specify what module code is generated. */
// "rootDir": "./", /* Specify the root folder within your source files. */
// "moduleResolution": "node10", /* Specify how TypeScript looks up a file from a given module specifier. */
// "baseUrl": "./", /* Specify the base directory to resolve non-relative module names. */
// "paths": {}, /* Specify a set of entries that re-map imports to additional lookup locations. */
// "rootDirs": [], /* Allow multiple folders to be treated as one when resolving modules. */
// "typeRoots": [], /* Specify multiple folders that act like './node_modules/@types'. */
// "types": [], /* Specify type package names to be included without being referenced in a source file. */
// "allowUmdGlobalAccess": true, /* Allow accessing UMD globals from modules. */
// "moduleSuffixes": [], /* List of file name suffixes to search when resolving a module. */
// "allowImportingTsExtensions": true, /* Allow imports to include TypeScript file extensions. Requires '--moduleResolution bundler' and either '--noEmit' or '--emitDeclarationOnly' to be set. */
// "rewriteRelativeImportExtensions": true, /* Rewrite '.ts', '.tsx', '.mts', and '.cts' file extensions in relative import paths to their JavaScript equivalent in output files. */
// "resolvePackageJsonExports": true, /* Use the package.json 'exports' field when resolving package imports. */
// "resolvePackageJsonImports": true, /* Use the package.json 'imports' field when resolving imports. */
// "customConditions": [], /* Conditions to set in addition to the resolver-specific defaults when resolving imports. */
// "noUncheckedSideEffectImports": true, /* Check side effect imports. */
// "resolveJsonModule": true, /* Enable importing .json files. */
// "allowArbitraryExtensions": true, /* Enable importing files with any extension, provided a declaration file is present. */
// "noResolve": true, /* Disallow 'import's, 'require's or '<reference>'s from expanding the number of files TypeScript should add to a project. */
/* JavaScript Support */
// "allowJs": true, /* Allow JavaScript files to be a part of your program. Use the 'checkJS' option to get errors from these files. */
// "checkJs": true, /* Enable error reporting in type-checked JavaScript files. */
// "maxNodeModuleJsDepth": 1, /* Specify the maximum folder depth used for checking JavaScript files from 'node_modules'. Only applicable with 'allowJs'. */
/* Emit */
// "declaration": true, /* Generate .d.ts files from TypeScript and JavaScript files in your project. */
// "declarationMap": true, /* Create sourcemaps for d.ts files. */
// "emitDeclarationOnly": true, /* Only output d.ts files and not JavaScript files. */
// "sourceMap": true, /* Create source map files for emitted JavaScript files. */
// "inlineSourceMap": true, /* Include sourcemap files inside the emitted JavaScript. */
// "noEmit": true, /* Disable emitting files from a compilation. */
// "outFile": "./", /* Specify a file that bundles all outputs into one JavaScript file. If 'declaration' is true, also designates a file that bundles all .d.ts output. */
// "outDir": "./", /* Specify an output folder for all emitted files. */
// "removeComments": true, /* Disable emitting comments. */
// "importHelpers": true, /* Allow importing helper functions from tslib once per project, instead of including them per-file. */
// "downlevelIteration": true, /* Emit more compliant, but verbose and less performant JavaScript for iteration. */
// "sourceRoot": "", /* Specify the root path for debuggers to find the reference source code. */
// "mapRoot": "", /* Specify the location where debugger should locate map files instead of generated locations. */
// "inlineSources": true, /* Include source code in the sourcemaps inside the emitted JavaScript. */
// "emitBOM": true, /* Emit a UTF-8 Byte Order Mark (BOM) in the beginning of output files. */
// "newLine": "crlf", /* Set the newline character for emitting files. */
// "stripInternal": true, /* Disable emitting declarations that have '@internal' in their JSDoc comments. */
// "noEmitHelpers": true, /* Disable generating custom helper functions like '__extends' in compiled output. */
// "noEmitOnError": true, /* Disable emitting files if any type checking errors are reported. */
// "preserveConstEnums": true, /* Disable erasing 'const enum' declarations in generated code. */
// "declarationDir": "./", /* Specify the output directory for generated declaration files. */
/* Interop Constraints */
// "isolatedModules": true, /* Ensure that each file can be safely transpiled without relying on other imports. */
// "verbatimModuleSyntax": true, /* Do not transform or elide any imports or exports not marked as type-only, ensuring they are written in the output file's format based on the 'module' setting. */
// "isolatedDeclarations": true, /* Require sufficient annotation on exports so other tools can trivially generate declaration files. */
// "allowSyntheticDefaultImports": true, /* Allow 'import x from y' when a module doesn't have a default export. */
"esModuleInterop": true, /* Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility. */
// "preserveSymlinks": true, /* Disable resolving symlinks to their realpath. This correlates to the same flag in node. */
"forceConsistentCasingInFileNames": true, /* Ensure that casing is correct in imports. */
/* Type Checking */
"strict": true, /* Enable all strict type-checking options. */
// "noImplicitAny": true, /* Enable error reporting for expressions and declarations with an implied 'any' type. */
// "strictNullChecks": true, /* When type checking, take into account 'null' and 'undefined'. */
// "strictFunctionTypes": true, /* When assigning functions, check to ensure parameters and the return values are subtype-compatible. */
// "strictBindCallApply": true, /* Check that the arguments for 'bind', 'call', and 'apply' methods match the original function. */
// "strictPropertyInitialization": true, /* Check for class properties that are declared but not set in the constructor. */
// "strictBuiltinIteratorReturn": true, /* Built-in iterators are instantiated with a 'TReturn' type of 'undefined' instead of 'any'. */
// "noImplicitThis": true, /* Enable error reporting when 'this' is given the type 'any'. */
// "useUnknownInCatchVariables": true, /* Default catch clause variables as 'unknown' instead of 'any'. */
// "alwaysStrict": true, /* Ensure 'use strict' is always emitted. */
// "noUnusedLocals": true, /* Enable error reporting when local variables aren't read. */
// "noUnusedParameters": true, /* Raise an error when a function parameter isn't read. */
// "exactOptionalPropertyTypes": true, /* Interpret optional property types as written, rather than adding 'undefined'. */
// "noImplicitReturns": true, /* Enable error reporting for codepaths that do not explicitly return in a function. */
// "noFallthroughCasesInSwitch": true, /* Enable error reporting for fallthrough cases in switch statements. */
// "noUncheckedIndexedAccess": true, /* Add 'undefined' to a type when accessed using an index. */
// "noImplicitOverride": true, /* Ensure overriding members in derived classes are marked with an override modifier. */
// "noPropertyAccessFromIndexSignature": true, /* Enforces using indexed accessors for keys declared using an indexed type. */
// "allowUnusedLabels": true, /* Disable error reporting for unused labels. */
// "allowUnreachableCode": true, /* Disable error reporting for unreachable code. */
/* Completeness */
// "skipDefaultLibCheck": true, /* Skip type checking .d.ts files that are included with TypeScript. */
"skipLibCheck": true /* Skip type checking all .d.ts files. */
}
}
package.jsonにスクリプトを追加します。
{
"name": "vips-image-processing",
"version": "1.0.0",
"description": "",
"main": "index.js",
"scripts": {
"start": "ts-node src/index.ts"
},
"keywords": [],
"author": "",
"license": "ISC",
"dependencies": {
"@types/node": "^22.10.2",
"@types/sharp": "^0.32.0",
"sharp": "^0.33.5",
"ts-node": "^10.9.2",
"typescript": "^5.7.2"
},
"devDependencies": {
"@types/jest": "^29.5.14",
"jest": "^29.7.0",
"ts-jest": "^29.2.5"
}
}
チャネル入れ替え
画像を読み込み、RGBをBGRの順に入れ替えよ。
画像の赤成分を取り出すには、以下のコードで可能。 cv2.imread()関数ではチャネルがBGRの順になることに注意！ これで変数redにimori.jpgの赤成分のみが入る。
import cv2
img = cv2.imread("imori.jpg")
red = img[:, :, 2].copy()
ディレクトリ構造
.
├── jest.config.js
├── main.jpeg
├── package-lock.json
├── package.json
├── src
│ ├── imageProcessor.test.ts
│ ├── imageProcessor.ts
│ └── index.ts
├── test-images
│ └── test.jpeg
└── tsconfig.json
入力画像
今回は下記の画像を入力として扱います。
Coding
ソースコードの作成します。
今回は画像処理のロジックは imageProcessor.ts に実装します。
mkdir src
touch src/index.ts
touch src/imageProcessor.ts
index.ts
imageProcessor に実装した swapRGBtoBGR へ入出力のファイルパスを渡す形で処理を実行させます。
import * as path from 'path';
import { swapRGBtoBGR } from './imageProcessor';
async function main() {
// __dirnameを使用して相対パスを解決
const inputPath = path.join(__dirname, '../main.jpeg');
const outputPath = path.join(__dirname, '../main_bgr.jpeg');
try {
console.log('画像処理を開始します...');
await swapRGBtoBGR(inputPath, outputPath);
console.log('処理が完了しました。出力ファイル:', outputPath);
} catch (error) {
console.error('プログラムの実行に失敗しました:', error);
}
}
main();
imageProcessor.ts
inputPath の画像を読み込み、RGBをBGRに変換して outputPath に画像を出力します。
import sharp from 'sharp';
export async function swapRGBtoBGR(inputPath: string, outputPath: string): Promise<void> {
try {
// 画像を読み込む
const image = await sharp(inputPath)
.raw() // RAWピクセルを取得
.toBuffer({ resolveWithObject: true });
// バッファーとメタ情報を取得
const { data, info } = image;
const { width, height, channels } = info;
// 新しいバッファーを作成
const newBuf = Buffer.alloc(data.length);
// RGB -> BGR の変換
for (let i = 0; i < data.length; i += channels) {
// Blue channel
newBuf[i] = data[i + 2];
// Green channel
newBuf[i + 1] = data[i + 1];
// Red channel
newBuf[i + 2] = data[i];
// Alpha channel (if exists)
if (channels === 4) {
newBuf[i + 3] = data[i + 3];
}
}
// 新しい画像を作成して保存
await sharp(newBuf, {
raw: {
width,
height,
channels
}
})
.toFile(outputPath);
console.log('チャネル入れ替えが完了しました');
} catch (error) {
console.error('画像処理中にエラーが発生しました:', error);
throw error;
}
}
Test
必要なライブラリをインストールします。
npm install --save-dev jest @types/jest ts-jest
Jest の設定ファイルを作成します。
touch jest.config.js
module.exports = {
preset: 'ts-jest',
testEnvironment: 'node',
roots: ['<rootDir>/src'],
testMatch: ['**/*.test.ts'],
verbose: true
};
次に、テストコードを実装します。
touch src/imageProcessor.test.ts
また、テスト実行用のスクリプトを package.json に追加します。
{
"scripts": {
"start": "ts-node src/index.ts",
"test": "jest",
"test:watch": "jest --watch",
"test:coverage": "jest --coverage"
}
}
次にテストコードを作成します。
touch src/imageProcessor.test.ts
import { existsSync, unlinkSync } from 'fs';
import { join } from 'path';
import sharp from 'sharp';
import { swapRGBtoBGR } from './imageProcessor';
describe('Image Processing Tests', () => {
const testInputPath = join(__dirname, '../test-images/test.jpeg');
const testOutputPath = join(__dirname, '../test-images/test-output.jpeg');
// 各テストの後にテスト出力ファイルを削除
afterEach(() => {
if (existsSync(testOutputPath)) {
unlinkSync(testOutputPath);
}
});
test('should verify test image exists', () => {
expect(existsSync(testInputPath)).toBe(true);
});
test('should successfully process image and create output file', async () => {
await expect(swapRGBtoBGR(testInputPath, testOutputPath)).resolves.not.toThrow();
expect(existsSync(testOutputPath)).toBe(true);
});
test('should correctly swap RGB to BGR', async () => {
await swapRGBtoBGR(testInputPath, testOutputPath);
// 入力画像のRGBデータを取得
const inputImage = await sharp(testInputPath)
.raw()
.toBuffer({ resolveWithObject: true });
// 出力画像のBGRデータを取得
const outputImage = await sharp(testOutputPath)
.raw()
.toBuffer({ resolveWithObject: true });
// サンプルピクセルのチェック（最初のピクセルのみ）
const inputChannels = {
r: inputImage.data[0],
g: inputImage.data[1],
b: inputImage.data[2]
};
const outputChannels = {
b: outputImage.data[0],
g: outputImage.data[1],
r: outputImage.data[2]
};
// 許容誤差を設定（例: ±2）
const tolerance = 2;
// 各チャネルの値が許容範囲内にあることを確認
expect(Math.abs(inputChannels.r - outputChannels.r)).toBeLessThanOrEqual(tolerance);
expect(Math.abs(inputChannels.g - outputChannels.g)).toBeLessThanOrEqual(tolerance);
expect(Math.abs(inputChannels.b - outputChannels.b)).toBeLessThanOrEqual(tolerance);
});
test('should throw error for non-existent input file', async () => {
const nonExistentPath = 'non-existent.jpeg';
await expect(swapRGBtoBGR(nonExistentPath, testOutputPath))
.rejects
.toThrow();
});
test('should maintain image dimensions and format', async () => {
await swapRGBtoBGR(testInputPath, testOutputPath);
const inputMetadata = await sharp(testInputPath).metadata();
const outputMetadata = await sharp(testOutputPath).metadata();
expect(outputMetadata.width).toBe(inputMetadata.width);
expect(outputMetadata.height).toBe(inputMetadata.height);
expect(outputMetadata.format).toBe(inputMetadata.format);
});
});
結果
RGBをBGRに変換することができました。
テストコードも用意することで、意図通りの実装になっているかを確認できますね。
| 入力 | 出力 |
|---|---|
|
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